Limulus

 ( Xiphosura ) 

Limulus is a genus of horseshoe crab, with one extant species, the Atlantic horseshoe crab ( Limulus polyphemus). One fossil species is currently assigned to the genus though several other species have been named, which have since been assigned to other genera.

Currently valid species include:

• Limulus polyphemus (Carl Linnaeus, 1758)
• Limulus coffiniextinction Reeside & Harris, 1952- Pierre Shale, United States, Late Cretaceous (Maastrichtian)

Doubtful species include:Dunlop, J. A., Penney, D. & Jekel, D. 2013. A summary list of fossil spiders and their relatives. In Platnick, N. I. (ed.) The world spider catalog, version 14.0 American Museum of Natural History, online at http://research.amnh.org/entomology/spiders/catalog/index.html

• Limulus nathorstiextinction Jackson, 1906- Jurassic, Sweden

Tentative species:

• "Limulus" decheniextinction Zinken, 1862- Paleogene, Germany (considered by some intermediate between Limulus and Tachypleus)